For the purpose of legal interception, an emergent call, location-based charging, cell-level locating, etc., the location of a User Equipment (UE) needs to be obtained at the network side. In Attach, Tracking Area Update (TAU), Service Request, X2 (an interface) HO (handover), S1 (an interface) HO and other procedures defined in the existing standards, cell-level identifier information of the UE can be obtained by a core network. A location reporting procedure is also defined in the standard to obtain current precise cell information of the UE. The location reporting procedure can inquire instantly about the identifier of a cell to which the UE is currently connected and can also configure an eNB (evolved Node B) to notify an MME (Mobility Management Entity) of the identifier of the cell immediately each time the UE changes its serving cell. For example, the MME sends a location reporting condition to the eNB in a Location Reporting Control message. The eNB sends the cell identifier information of the UE to the MME in a Location Report message when the location reporting condition is satisfied.
If the MME supports a function of “location information change reporting”, then a PGW (Packet Data Network Gateway) will be notified of this through an SGW (Serving Gateway). When the PGW knows the MME supporting the function of “location information change reporting”, the PGW can request the MME to notify the PGW when there is a change in location information of the UE, to thereby achieve location-based charging.
In a Long Term Evolution-Advanced (LTE-A) system, a Relay Node (RN) has been introduced to extend network coverage. The RN is connected wirelessly to a Donor Evolved Node B (DeNB). The cell to which the RN is connected is called a donor cell, and a cell to which the UE is connected is called the serving cell for the concerned UE. In a high speed moving environment, the RN can be deployed e.g. in a railway, for the purpose of reducing the handover rates of the UEs, and improving a signal quality inside a train. In this case, the UE moves from a place A to a place B, but in the serving RN is not changed, that is, there is no change in serving cell of the UE. If serving cell information of the UE is reported as in the prior art, then the core network may assume from the service cell information that the UE has not moved significantly although the UE indeed has moved far away. Apparently, in the prior art, the UE may be inaccurately located just according to the severing cell information, thus affecting accurate charging for the UE.